Fuel cell module

ABSTRACT

A fuel cell module includes a first area where an exhaust gas combustor and a start-up combustor are provided, an annular second area disposed around the first area where a heat exchanger is provided, an annular third area disposed around the second area where a reformer is provided, and an annular fourth area disposed around the third area where an evaporator is provided. A stress absorber for absorbing heat stress is provided in at least one of the first area, the second area, the third area, and the fourth area.

TECHNICAL FIELD

The present invention relates to a fuel cell module including a fuelcell stack formed by stacking a plurality of fuel cells for generatingelectricity by electrochemical reactions between a fuel gas and anoxygen-containing gas.

BACKGROUND ART

Typically, a solid oxide fuel cell (SOFC) employs a solid electrolytemade of an ion-conductive oxide such as stabilized zirconia. Theelectrolyte is interposed between an anode and a cathode to form anelectrolyte electrode assembly (hereinafter also referred to as an MEA).The electrolyte electrode assembly is interposed between separators.During use thereof, generally, a predetermined number of the electrolyteelectrode assemblies and the separators are stacked together to form afuel cell stack.

As a system including this type of fuel cell stack, for example, thefuel cell battery disclosed in Japanese Laid-Open Patent Publication No.2001-236980 (hereinafter referred to as conventional technique 1) isknown. As shown in FIG. 14, the fuel cell battery includes a fuel cellstack 1 a, and a heat insulating sleeve 2 a provided at one end of thefuel cell stack 1 a. A reaction device 4 a is provided in the heatinsulating sleeve 2 a. The reaction device 4 a includes a heat exchanger3 a.

In the reaction device 4 a, as a treatment for a liquid fuel, partialoxidation reforming, which does not use water, is performed. After theliquid fuel is evaporated by an exhaust gas, the liquid fuel passesthrough a feeding point 5 a, which forms part of the heat exchanger 3 a.The fuel contacts an oxygen carrier gas heated by the exhaust gas toinduce partial oxidation reforming, and thereafter, the fuel is suppliedto the fuel cell stack 1 a.

Further, as shown in FIG. 15, the solid oxide fuel cell disclosed inJapanese Laid-Open Patent Publication No. 2010-504607 (PCT) (hereinafterreferred to as conventional technique 2) has a heat exchanger 2 bincluding a cell core 1 b. The heat exchanger 2 b heats air at thecathode utilizing waste heat.

Further, as shown in FIG. 16, the fuel cell system disclosed in JapaneseLaid-Open Patent Publication No. 2004-288434 (hereinafter referred to asconventional technique 3) includes a first area 1 c having a verticallyextending columnar shape, and an annular second area 2 c disposed aroundthe first area 1 c, an annular third area 3 c disposed around the secondarea 2 c, and an annular fourth area 4 c disposed around the third area3 c.

A burner 5 c is provided in the first area 1 c, and a reforming pipe 6 cis provided in the second area 2 c. A water evaporator 7 c is providedin the third area 3 c, and a CO shift converter 8 c is provided in thefourth area 4 c.

SUMMARY OF INVENTION

In conventional technique 1, temperature distribution in the reactiondevice 4 a tends to be non-uniform due to the heat of the exhaust gas.Thus, if it is attempted to improve the heat exchange efficiency, alarge temperature difference is produced in a vertical direction or in alateral direction. Thus, heat stress is provided, and the durability isdegraded.

Further, in conventional technique 2, since the heat exchanger 2 bcontaining the cell core 1 b is provided, temperature distribution inthe fuel cell tends to be non-uniform. Thus, if it is attempted toimprove the heat exchange efficiency, a large temperature difference isproduced in a vertical direction or in a lateral direction. Thus, heatstress is provided, and the durability is degraded.

Further, in conventional technique 3, the first area 1 c where theburner 5 c is provided, the second area 2 c where the reforming pipe 6 cis provided, the third area 3 c where the water evaporator 7 c isprovided, and the fourth area 4 c where the CO shift converter 8 c isprovided are formed concentrically around the center. Thus, thetemperature distribution in the fuel cell tends to be non-uniform. Thus,if it is attempted to improve the heat exchange efficiency, a largetemperature difference is produced in a vertical direction (axially) orin a lateral direction (radially). Thus, heat stress is produced, andthe durability is degraded.

The present invention has been made to solve the aforementioned problemsof this type, and has the object of providing a fuel cell module havinga simple and compact structure in which improvement in the heatefficiency is achieved, thermally self-sustaining operation isfacilitated, and improvement in the durability is achieved.

The present invention relates to a fuel cell module comprising a fuelcell stack formed by stacking fuel cells for generating electricity byelectrochemical reactions between a fuel gas and an oxygen-containinggas, a reformer for reforming a mixed gas of water vapor and a raw fuelchiefly containing hydrocarbon to produce the fuel gas supplied to thefuel cell stack, an evaporator for evaporating water, and supplying thewater vapor to the reformer, a heat exchanger for raising temperature ofthe oxygen-containing gas by heat exchange with combustion gas, andsupplying the oxygen-containing gas to the fuel cell stack, an exhaustgas combustor for combusting the fuel gas discharged from the fuel cellstack as a fuel exhaust gas and the oxygen-containing gas dischargedfrom the fuel cell stack as an oxygen-containing exhaust gas to therebyproduce the combustion gas, and a start-up combustor for combusting theraw fuel and the oxygen-containing gas to thereby produce the combustiongas.

The fuel cell module further comprises a first area where the exhaustgas combustor and the start-up combustor are provided, an annular secondarea disposed around the first area where one of the reformer and theheat exchanger is provided, an annular third area disposed around thesecond area where another of the reformer and the heat exchanger isprovided, an annular fourth area disposed around the third area wherethe evaporator is provided, a first partition plate provided between thefirst area and the second area, a second partition plate providedbetween the second area and the third area, and a third partition plateprovided between the third area and the fourth area.

Further, a stress absorber for absorbing heat stress is provided in atleast one of the first area, the second area, the third area, and thefourth area.

In the present invention, the annular second area is disposed at thecenter around the first area where the exhaust gas combustor and thestart-up combustor are provided, the annular third area is disposedaround the second area, and the annular fourth, area is disposed aroundthe third area. In such a structure, hot temperature equipment with alarge heat demand can be provided on the inside, and low temperatureequipment with a small heat demand can be provided on the outside.Accordingly, an improvement in heat efficiency is achieved, and athermally self-sustaining operation is facilitated. Further, a simpleand compact structure is achieved.

Further, the stress absorber for absorbing heat stress is provided in atleast one of the first area, the second area, the third area, and thefourth area. In the structure, when the FC peripheral equipmentincluding the reformer, the evaporator, the heat exchanger, the exhaustgas combustor, and the start-up combustor are expanded by heat, thestress absorber absorbs the heat stress in a radial direction and anaxial direction. Accordingly, it becomes possible to suitably suppressdegradation of the durability in the FC peripheral equipment due to theheat stress.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram schematically showing the structure of a fuel cellsystem including a fuel cell module according to a first embodiment ofthe present invention;

FIG. 2 is a perspective view with partial omission showing FC peripheralequipment of the fuel cell module;

FIG. 3 is an exploded perspective view showing main components of the FCperipheral equipment;

FIG. 4 is an enlarged perspective view showing main components of the FCperipheral equipment;

FIG. 5 is a view showing gas flows of a combustion gas in the FCperipheral equipment;

FIG. 6 is a view illustrating temperature distribution in the FCperipheral equipment;

FIG. 7 is a diagram schematically showing the structure of a fuel cellsystem including a fuel cell module according to a second embodiment ofthe present invention;

FIG. 8 is a perspective view with partial omission showing FC peripheralequipment of the fuel cell module;

FIG. 9 is a view showing gas flows of a combustion gas in the FCperipheral equipment;

FIG. 10 is a view illustrating another shape of a stress absorber;

FIG. 11 is a view illustrating still another shape of the stressabsorber;

FIG. 12 is a view illustrating still another shape of the stressabsorber;

FIG. 13 is a view illustrating still another shape of the stressabsorber;

FIG. 14 is a view schematically showing the fuel cell battery disclosedin conventional technique 1;

FIG. 15 is a partially cutaway perspective view, showing the solid oxidefuel cell disclosed in conventional technique 2; and

FIG. 16 is a view schematically showing the fuel cell system disclosedin conventional technique 3.

DESCRIPTION OF EMBODIMENTS

As shown in FIG. 1, a fuel cell system 10 includes a fuel cell module 12according to a first embodiment of the present invention. The fuel cellsystem 10 is used in various applications, including stationary andmobile applications. For example, the fuel cell system 10 may be mountedon a vehicle.

The fuel cell system 10 includes the fuel cell module (SOFC module) 12for generating electrical energy used for power generation byelectrochemical reactions between a fuel gas (a gas produced by mixinghydrogen gas, methane, and carbon monoxide) and an oxygen-containing gas(air), a raw fuel supply apparatus (including a fuel gas pump) 14 forsupplying a raw fuel (e.g., city gas) to the fuel cell module 12, anoxygen-containing gas supply apparatus (including an air pump) 16 forsupplying the oxygen-containing gas to the fuel cell module 12, a watersupply apparatus (including a water pump) 18 for supplying water to thefuel cell module 12, and a control device 20 for controlling the amountof electrical energy generated in the fuel cell module 12.

The fuel cell module 12 includes a fuel cell stack 24 formed by stackinga plurality of solid oxide fuel cells 22 in a vertical direction (or ahorizontal direction). The fuel cell 22 includes an electrolyteelectrode assembly (MEA) 32. The electrolyte electrode assembly 32includes a cathode 28, an anode 30, and an electrolyte 26 interposedbetween the cathode 28 and the anode 30. For example, the electrolyte 26is made of an ion-conductive oxide such as stabilized zirconia.

A cathode side separator 34 and an anode side separator 36 are providedon both sides of the electrolyte electrode assembly 32. Anoxygen-containing gas flow field 38 for supplying the oxygen-containinggas to the cathode 28 is formed in the cathode side separator 34, and afuel gas flow field 40 for supplying the fuel gas to the anode 30 isformed in the anode side separator 36. Various types of conventionalSOFCs can be adopted as the fuel cell 22.

The operating temperature of the fuel cell 22 is high, on the order ofseveral hundred ° C. Methane in the fuel gas is reformed at the anode 30to obtain hydrogen and CO, and hydrogen and CO are supplied to a portionof the electrolyte 26 adjacent to the anode 30.

An oxygen-containing gas supply passage 42 a, an oxygen-containing gasdischarge passage 42 b, a fuel gas supply passage 44 a, and a fuel gasdischarge passage 44 b extend through the fuel cell stack 24. Theoxygen-containing gas supply passage 42 a is connected to an inlet ofeach oxygen-containing gas flow field 38, the oxygen-containing gasdischarge passage 42 b is connected to an outlet of eachoxygen-containing gas flow field 38, the fuel gas supply passage 44 a isconnected to an inlet of each fuel gas flow field 40, and the fuel gasdischarge passage 44 b is connected to an outlet of each fuel gas flowfield 40.

The fuel cell module 12 includes a reformer 46 for reforming a mixed gasof water vapor and raw fuel which chiefly contains hydrocarbon (e.g.,city gas) to thereby produce a fuel gas that is supplied to the fuelcell stack 24, an evaporator 48 for evaporating water and supplyingwater vapor to the reformer 46, a heat exchanger 50 for raising thetemperature of the oxygen-containing gas through heat exchange with acombustion gas, and supplying the oxygen-containing gas to the fuel cellstack 24, an exhaust gas combustor 52 for combusting the fuel gas, whichis discharged as a fuel exhaust gas from the fuel cell stack 24, and theoxygen-containing gas, which is discharged as an oxygen-containingexhaust gas from the fuel cell stack 24, to thereby produce thecombustion gas, and a start-up combustor 54 for combusting the raw fueland the oxygen-containing gas to thereby produce the combustion gas.

Basically, the fuel cell module 12 is made up of the fuel cell stack 24and FC (fuel cell) peripheral equipment 56. FC peripheral equipment 56includes the reformer 46, the evaporator 48, the heat exchanger 50, theexhaust gas combustor 52, and the start-up combustor 54.

As shown in FIG. 2, the FC peripheral equipment 56 includes a first areaR1 comprising, e.g., a circular opening where the exhaust gas combustor52 and the start-up combustor 54 are provided, an annular second area R2formed around the first area R1 where the heat exchanger 50 is provided,an annular third area R3 formed around the second area R2 where thereformer 46 is provided, and an annular fourth area R4 formed around thethird area R3 where the evaporator 48 is provided.

As shown in FIGS. 2 and 3, the start-up combustor 54 includes an airsupply pipe 57 and a raw fuel supply pipe 58. The start-up combustor 54includes an ejector function for generating a negative pressure forsucking raw fuel in the raw fuel supply pipe 58 by flow of air suppliedfrom the air supply pipe 57.

As shown in FIGS. 2 and 4, the FC peripheral equipment 56 includes afirst partition plate 60 a provided between the first area R1 and thesecond area R2, a second partition plate 60 b provided between thesecond area R2 and the third area R3, and a third partition plate 60 cprovided between the third area R3 and the fourth area R4. Also, afourth partition plate 60 d is disposed around the fourth area R4 as anouter plate. For example, the first partition plate 60 a to the fourthpartition plate 60 d are made of stainless steel plates.

As shown in FIGS. 2 and 3, the exhaust gas combustor 52 is providedinside the first partition plate 60 a that contains the start-upcombustor 54. The first partition plate 60 a has a cylindrical shape. Aplurality of first combustion gas holes 62 a are formed along an outercircumferential portion of the first partition plate 60 a, adjacent toan end of the first partition plate 60 a close to the fuel cell stack24.

A plurality of second combustion gas holes 62 b are formed adjacent toan end of the second partition plate 60 b opposite from the fuel cellstack 24. A plurality of third combustion gas holes 62 c are formedadjacent to an end of the third partition plate 60 c close to the fuelcell stack 24. A plurality of fourth combustion gas holes 62 d areformed adjacent to an end of the fourth partition plate 60 d oppositefrom the fuel cell stack 24. The combustion gas is discharged to theexterior through the fourth combustion gas holes 62 d.

One end of an oxygen-containing exhaust gas channel 63 a and one end ofan fuel exhaust gas channel 63 b are provided respectively on the firstpartition plate 60 a. Combustion gas is produced inside the firstpartition plate 60 a by a combustion reaction between the fuel gas (morespecifically, a fuel exhaust gas) and the oxygen-containing gas (morespecifically, an oxygen-containing exhaust gas).

As shown in FIG. 1, the other end of the oxygen-containing exhaust gaschannel 63 a is connected to the oxygen-containing gas discharge passage42 b of the fuel cell stack 24, and the other end of the fuel exhaustgas channel 63 b is connected to the fuel gas discharge passage 44 b ofthe fuel cell stack 24.

As shown in FIGS. 2 and 3, the heat exchanger 50 includes a plurality ofheat exchange pipes (heat transmission pipes) 64 disposed around thefirst partition plate 60 a. The heat exchange pipes 64 are fixed to afirst inner ring 66 a at one end (i.e., the other end opposite from thefuel cell stack 24; hereinafter, in the same manner, the other endopposite from the fuel cell stack 24 is referred to as “one end”). Theheat exchange pipes 64 are fixed to a first inner ring 66 b at the otherend (i.e., one end closer to the fuel cell stack 24; hereinafter, in thesame manner, the one end closer to the fuel cell stack 24 is referred toas an “other end”).

A first outer ring 68 a is provided on the outside of the first innerring 66 a, and a first outer ring 68 b is provided on the outside of thefirst inner ring 66 b. The first inner rings 66 a, 66 b and the firstouter rings 68 a, 68 b are fixed respectively to the outercircumferential surface of the first partition plate 60 a, and to theinner circumferential surface of the second partition plate 60 b.

An annular oxygen-containing gas supply chamber 70 a is formed betweenthe first inner ring 66 a and the first outer ring 68 a, andoxygen-containing gas is supplied to the oxygen-containing gas supplychamber 70 a. An annular oxygen-containing gas discharge chamber 70 b isformed between the first inner ring 66 b and the first outer ring 68 b,and heated oxygen-containing gas is discharged into theoxygen-containing gas discharge chamber 70 b (see FIGS. 2 to 4).Opposite ends of each of the heat exchange pipes 64 open respectivelyinto the oxygen-containing gas supply chamber 70 a and theoxygen-containing gas discharge chamber 70 b.

An oxygen-containing gas supply pipe 72 is connected to theoxygen-containing gas supply chamber 70 a. One end of anoxygen-containing gas channel 74 is connected to the oxygen-containinggas discharge chamber 70 b, whereas the other end of theoxygen-containing gas channel 74 is connected to the oxygen-containinggas supply passage 42 a of the fuel cell stack 24 (see FIG. 1).

The reformer 46 is a preliminary reformer for reforming higherhydrocarbon (C₂₊) such as ethane (C₂H₆), propane (C₃H₈), and butane(C₄H₁₀) in the city gas (raw fuel), to thereby produce by steamreforming a fuel gas chiefly containing methane (CH₄), hydrogen, and CO.The operating temperature of the reformer 46 is several hundred ° C.

As shown in FIGS. 2 and 3, the reformer 46 includes a plurality ofreforming pipes (heat transmission pipes) 76 disposed around the heatexchanger 50. The reforming pipes 76 are fixed to a second inner ring 78a at one end thereof, and are fixed to a second inner ring 78 b at theother end thereof.

A second outer ring 80 a is provided outside of the second inner ring 78a, and a second outer ring 80 b is provided outside of the second innerring 78 b. The second inner rings 78 a, 78 b and the second outer rings80 a, 80 b are fixed respectively to the outer circumferential surfaceof the second partition plate 60 b, and to the inner circumferentialsurface of the third partition plate 60 c.

An annular mixed gas supply chamber 82 a is formed between the secondinner ring 78 a and the second outer ring 80 a. A mixed gas of raw fueland water vapor is supplied to the mixed gas supply chamber 82 a. Anannular reformed gas discharge chamber 82 b is formed between the secondinner ring 78 b and the second outer ring 80 b. The produced fuel gas(reformed gas) is discharged to the reformed gas discharge chamber 82 b.

Opposite ends of each of the reforming pipes 76 open respectively intothe mixed gas supply chamber 82 a and the reformed gas discharge chamber82 b. Reforming catalyst pellets 84 fill inside of each of the reformingpipes 76. Metal meshes 86 are disposed on opposite ends of the reformingpipes 76 for supporting and maintaining the catalyst pellets 84 insidethe reforming pipes 76.

A raw fuel supply channel 88 is connected to the mixed gas supplychamber 82 a, and a later-described evaporation return pipe 102 isconnected to a middle position of the raw fuel supply channel 88. Oneend of a fuel gas channel 90 is connected to the reformed gas dischargechamber 82 b, whereas the other end of the fuel gas channel 90 isconnected to the fuel gas supply passage 44 a of the fuel cell stack 24(see FIG. 1).

The evaporator 48 includes evaporation pipes (heat transmission pipes)92 disposed outside of and around the reformer 46. The evaporation pipes92 are fixed to a third inner ring 94 a at one end thereof, and arefixed to a third inner ring 94 b at the other end thereof.

A third outer ring 96 a is provided outside of the third inner ring 94a, and a third outer ring 96 b is provided outside of the third innerring 94 b. The third inner rings 94 a, 94 b and the third outer rings 96a, 96 b are fixed to the outer circumferential surface of the thirdpartition plate 60 c, and to the inner circumferential surface of thefourth partition plate 60 d.

An annular water supply chamber 98 a is formed between the third innerring 94 a and the third outer ring 96 a. Water is supplied to the watersupply chamber 98 a. An annular water vapor discharge chamber 98 b isformed between the third inner ring 94 b and the third outer ring 96 b.Water vapor is discharged to the water vapor discharge chamber 98 b.Opposite ends of the evaporation pipes 92 open into the water supplychamber 98 a and the water vapor discharge chamber 98 b, respectively.

A water channel 100 is connected to the water supply chamber 98 a. Oneend of the evaporation return pipe 102, which includes at least oneevaporation pipe 92, is provided in the water vapor discharge chamber 98b, whereas the other end of the evaporation return pipe 102 is connectedto a middle position of the raw fuel supply channel 88 (see FIG. 1). Theraw fuel supply channel 88 has an ejector function for generating anegative pressure as a result of the raw fuel flowing therein, forthereby sucking the water vapor.

In the present invention, a stress absorber 103 for absorbing heatstress is provided in at least one of the first area R1, the second areaR2, the third area R3, and the fourth area R4 (in particular, an areawhich is likely to be exposed to high heat).

The stress absorber 103 is provided in at least one of theoxygen-containing gas discharge chamber 70 b, the reformed gas dischargechamber 82 b, and the water vapor discharge chamber 98 b. In the firstembodiment, the stress absorber 103 is provided in each of the innerring 66 b and the outer ring 68 b of the oxygen-containing gas dischargechamber 70 b, the inner ring 78 b and the outer ring 80 b of thereformed gas discharge chamber 82 b, and the inner ring 94 b and theouter ring 96 b of the water vapor discharge chamber 98 b (see FIG. 4).

Further, the stress absorber 103 is provided in at least one of theoxygen-containing gas supply chamber 70 a, the mixed gas supply chamber82 a, and the water supply chamber 98 a. In the first embodiment, thestress absorber 103 is provided in each of the inner ring 66 a and theouter ring 68 a of the oxygen-containing gas supply chamber 70 a, theinner ring 78 a and the outer ring 80 a of the mixed gas supply chamber82 a, and the inner ring 94 a and the outer ring 96 a of the watersupply chamber 98 a (see FIG. 2). For example, the inner rings 66 a, 66b, 78 a, 78 b, 94 a, and 94 b and the outer rings 68 a, 68 b, 80 a, 80b, 96 a, 96 b are made of stainless steel plates.

In particular, as shown in FIG. 4, in the oxygen-containing gasdischarge chamber 70 b exposed to the hot combustion gas, an innercurved portion 103 ai and an outer curved portion 103 ao each having asemicircular shape in cross section are formed at inner and outerpositions of the inner ring 66 b. Likewise, in the oxygen-containing gasdischarge chamber 70 b, an inner curved portion 103 bi and an outercurved portion 103 bo each having a semicircular shape in cross sectionare formed at inner and outer positions of the outer ring 68 b.

The inner curved portions 103 ai, 103 bi and the outer curved portions103 ao, 103 bo function as springs with low rigidity capable ofabsorbing displacement to form the stress absorber 103. Only the innercurved portions 103 ai, 103 bi or the outer curved portions 103 ao, 103bo may be provided. The other inner rings 66 a, 78 a, 78 b, 94 a, 94 band the other outer rings 68 a, 80 a, 80 b, 96 a, 96 b have the samestructure as the inner ring 66 b and the outer ring 68 b, and thedetailed descriptions thereof are omitted.

As shown in FIG. 1, the raw fuel supply apparatus 14 includes a raw fuelchannel 104. The raw fuel channel 104 branches through a raw fuelregulator valve 106 into the raw fuel supply channel 88 and the raw fuelsupply pipe 58. A desulfurizer 108 for removing sulfur compounds in thecity gas (raw fuel) is provided in the raw fuel supply channel 88.

The oxygen-containing gas supply apparatus 16 includes anoxygen-containing gas channel 110. The oxygen-containing gas channel 110branches through an oxygen-containing gas regulator valve 112 into theoxygen-containing gas supply pipe 72 and the air supply pipe 57. Thewater supply apparatus 18 is connected to the evaporator 48 through thewater channel 100.

In the first embodiment, as schematically shown in FIG. 5, a firstcombustion gas channel 116 a, which serves as a passage for thecombustion gas, is formed in the first area R1, a second combustion gaschannel 116 b, which serves as a passage for the combustion gas in thedirection of the arrow A1, is formed in the second area R2, a thirdcombustion gas channel 116 c, which serves as a passage for thecombustion gas in the direction of the arrow A2, is formed in the thirdarea R3, and a fourth combustion gas channel 116 d, which serves as apassage for the combustion gas in the direction of the arrow A1, isformed in the fourth area R4.

Next, operations of the fuel cell system 10 will be described below.

At the time of starting operation of the fuel cell system 10, air(oxygen-containing gas) and raw fuel are supplied to the start-upcombustor 54. Specifically, air is supplied to the oxygen-containing gaschannel 110 by the operation of the air pump of the oxygen-containinggas supply apparatus 16. More specifically, air is supplied to the airsupply pipe 57 by adjusting the opening angle of the oxygen-containinggas regulator valve 112.

In the meantime, in the raw fuel supply apparatus 14, by operation ofthe fuel gas pump, for example, raw fuel such as city gas (containingCH₄, C₂H₆, C₃H₈, and C₄H₁₀) is supplied to the raw fuel channel 104. Rawfuel is supplied into the raw fuel supply pipe 58 by regulating theopening angle of the raw fuel regulator valve 106. The raw fuel is mixedwith air, and is supplied into the start-up combustor 54 (see FIG. 2).

Thus, mixed gas of raw fuel and air is supplied into the start-upcombustor 54, and the mixed gas is ignited to start combustion.Therefore, in the exhaust gas combustor 52, which is connected directlyto the start-up combustor 54, the combustion gas from the start-upcombustor 54 flows into the first partition plate 60 a.

As shown in FIG. 5, the plurality of first combustion gas holes 62 a areformed at the end of the first partition plate 60 a close to the fuelcell stack 24. Thus, combustion gas supplied into the first partitionplate 60 a passes through the first combustion gas holes 62 a, whereuponthe combustion gas flows from the first area R1 into the second area R2.

In the second area R2, the combustion gas flows in the direction of thearrow A1, and then the combustion gas flows through the secondcombustion gas holes 62 b formed in the second partition plate 60 b andinto the third area R3. In the third area R3, the combustion gas flowsin the direction of the arrow A2, and then the combustion gas flowsthrough the third combustion gas holes 62 c formed in the thirdpartition plate 60 c and into the fourth area R4. In the fourth area R4,the combustion gas flows in the direction of the arrow A1, and then thecombustion gas is discharged to the exterior through the fourthcombustion gas holes 62 d formed in the fourth partition plate 60 d.

The heat exchanger 50 is provided in the second area R2, the reformer 46is provided in the third area R3, and the evaporator 48 is provided inthe fourth area R4. Thus, combustion gas, which is discharged from thefirst area R1, heats the heat exchanger 50, then heats the reformer 46,and then heats the evaporator 48.

After the temperature of the fuel cell module 12 has been raised to apredetermined temperature, the oxygen-containing gas is supplied intothe heat exchanger 50, and the mixed gas of raw fuel and water vapor issupplied into the reformer 46.

More specifically, the opening angle of the oxygen-containing gasregulator valve 112 is adjusted such that the flow rate of air suppliedto the oxygen-containing gas supply pipe 72 is increased. In addition,the opening angle of the raw fuel regulator valve 106 is adjusted suchthat the flow rate of the raw fuel supplied to the raw fuel supplychannel 88 is increased. Further, by operation of the water supplyapparatus 18, water is supplied to the water channel 100.

Thus, as shown in FIGS. 2 and 3, air that has flowed into the heatexchanger 50 is temporarily supplied to the oxygen-containing gas supplychamber 70 a. While air moves inside the heat exchange pipes 64, the airis heated by means of heat exchange with the combustion gas suppliedinto the second area R2. After the heated air has temporarily beensupplied to the oxygen-containing gas discharge chamber 70 b, the air issupplied to the oxygen-containing gas supply passage 42 a of the fuelcell stack 24 through the oxygen-containing gas channel 74 (see FIG. 1).

In the fuel cell stack 24, after the heated air has flowed through theoxygen-containing gas flow field 38, the oxygen-containing gas isdischarged from the oxygen-containing gas discharge passage 42 b andinto the oxygen-containing exhaust gas channel 63 a. Theoxygen-containing exhaust gas channel 63 a opens toward the inside ofthe first partition plate 60 a of the exhaust gas combustor 52, so thatthe oxygen-containing exhaust gas can flow into the first partitionplate 60 a.

Further, as shown in FIG. 1, water from the water supply apparatus 18 issupplied to the evaporator 48. After sulfur has been removed from theraw fuel at the desulfurizer 108, the raw fuel flows through the rawfuel supply channel 88 and moves toward the reformer 46.

In the evaporator 48, after water has temporarily been supplied to thewater supply chamber 98 a, while the water moves inside the evaporationpipes 92, the water is heated by means of the combustion gas that flowsthrough the fourth area R4, and the water is vaporized. After watervapor has flowed into the water vapor discharge chamber 98 b, the watervapor is supplied to the evaporation return pipe 102, which is connectedto the water vapor discharge chamber 98 b. Thus, water vapor flowsinside the evaporation return pipe 102, and further flows into the rawfuel supply channel 88. Then, the water vapor becomes mixed with the rawfuel to produce the mixed gas.

The mixed gas from the raw fuel supply channel 88 is temporarilysupplied to the mixed gas supply chamber 82 a of the reformer 46. Themixed gas moves inside the reforming pipes 76. In the meantime, themixed gas is heated by means of the combustion gas that flows throughthe third area R3. Steam reforming is performed by the catalyst pellets84. After removal (reforming) of C₂₊ hydrocarbons, a reformed gaschiefly containing methane is obtained.

After the reformed gas is heated, the reformed gas is temporarilysupplied as a fuel gas to the reformed gas discharge chamber 82 b.Thereafter, the fuel gas is supplied to the fuel gas supply passage 44 aof the fuel cell stack 24 through the fuel gas channel 90 (see FIG. 1).

In the fuel cell stack 24, after the heated fuel gas has flowed throughthe fuel gas flow field 40, the fuel gas is discharged from the fuel gasdischarge passage 44 b and into the fuel exhaust gas channel 63 b. Thefuel exhaust gas channel 63 b opens toward the inside of the firstpartition plate 60 a of the exhaust gas combustor 52, so that the fuelexhaust gas can be supplied into the first partition plate 60 a.

Under a heating operation of the start-up combustor 54, when thetemperature of the fuel gas in the exhaust gas combustor 52 exceeds theself-ignition temperature, combustion is initiated in the firstpartition plate 60 a between the oxygen-containing exhaust gas and thefuel exhaust gas.

In the first embodiment, the FC peripheral equipment 56 includes thefirst area R1 where the exhaust gas combustor 52 and the start-upcombustor 54 are provided, the annular second area R2 disposed aroundthe first area R1 where the heat exchanger 50 is provided, the annularthird area R3 disposed around the second area R2 where the reformer 46is provided, and the annular fourth area R4 disposed around the thirdarea R3 where the evaporator 48 is provided.

More specifically, the annular second area R2 is disposed in the centeraround the first area R1, the annular third area R3 is disposed aroundthe second area R2, and the annular fourth area R4 is disposed aroundthe third area R3. In such a structure, hot temperature equipment with alarge heat demand such as the heat exchanger 50 (and the reformer 46)can be provided on the inside, whereas low temperature equipment with asmall heat demand such as the evaporator 48 can be provided on theoutside.

For example, the heat exchanger 50 requires a temperature in a range of550° C. to 650° C., and the reformer 46 requires a temperature in arange of 550° C. to 600° C. Further, the evaporator 48 requires atemperature in a range of 150° C. to 200° C.

Thus, an improvement in heat efficiency is achieved, and a thermallyself-sustaining operation is facilitated. Further, a simple and compactstructure can be achieved. In particular, since the heat exchanger 50 isprovided inside the reformer 46 in an environment where the A/F(air/fuel gas) ratio is relatively low, the reformer 46, which issuitable for carrying out reforming at low temperatures, can be usedadvantageously. The phrase “thermally self-sustaining operation” hereinimplies an operation in which the operating temperature of the fuel cell22 is maintained using only heat generated in the fuel cell 22 itself,without supplying additional heat from the exterior.

Further, the stress absorber 103 for absorbing heat stress is providedin at least one of the first area R1, the second area R2, the third areaR3, and the fourth area R4. In the structure, when the FC peripheralequipment 56 including the reformer 46, the evaporator 48, the heatexchanger 50, the exhaust gas combustor 52, and the start-up combustor54 is expanded by heat, the stress absorber 103 absorbs the heat stressin a radial direction. Accordingly, it becomes possible to suitablysuppress degradation of the durability in the FC peripheral equipment 56due to the heat stress.

In particular, the stress absorber 103 is provided in at least one ofthe oxygen-containing gas discharge chamber 70 b, the reformed gasdischarge chamber 82 b, and the water vapor discharge chamber 98 b. Inthe first embodiment, the stress absorber 103 is provided in each of theinner ring 66 b and the outer ring 68 b of the oxygen-containing gasdischarge chamber 70 b, the inner ring 78 b and the outer ring 80 b ofthe reformed gas discharge chamber 82 b, and the inner ring 94 b and theouter ring 96 b of the water vapor discharge chamber 98 b. Further, thestress absorber 103 is provided in at least one of the oxygen-containinggas supply chamber 70 a, the mixed gas supply chamber 82 a, and thewater supply chamber 98 a. In the first embodiment, the stress absorber103 is provided in each of the inner ring 66 a and the outer ring 68 aof the oxygen-containing gas supply chamber 70 a, the inner ring 78 aand the outer ring 80 a of the mixed gas supply chamber 82 a, and theinner ring 94 a and the outer ring 96 a of the water supply chamber 98a.

As shown in FIG. 6, in the FC peripheral equipment 56, the temperaturetends to be decreased from the first area R1 to the fourth area R4 (inthe direction indicated by the arrow B), and decreased in the directionaway from the fuel cell stack 24 (in the direction indicated by thearrow A). Thus, in the FC peripheral equipment 56, the temperaturedifference tends to occur in the radial direction and axial direction.

Due to the temperature difference in the radial direction, the heatexpansion becomes small toward the outside, and stress is generatedbetween both sides of partitions (the first to fourth partition plates60 a to 60 d). Due to the temperature difference in the axial direction,pipes (the heat exchange pipe 64, the reforming pipe 76, and theevaporation pipe 92) are inclined to produce stress at connectingpotions of the pipes.

Further, at least in correspondence with the position exposed to the hotexhaust gas, the stress absorber 103 is provided. Thus, when the FCperipheral equipment 56 is expanded by heat, the stress absorber 103 canabsorb the heat stress in the radial direction and the heat stress inthe axial direction. Accordingly, it becomes possible to suitablysuppress degradation of the durability in the FC peripheral equipment 56due to the heat stress.

Further, in the oxygen-containing gas discharge chamber 70 b exposed tothe hot combustion gas, as shown in FIG. 4, for the stress absorber 103,the inner curved portion 103 ai and the outer curved portion 103 ao eachhaving a semicircular shape in cross section are formed at inner andouter positions of the first inner ring 66 b. Thus, with the simple andeconomical structure, the stress absorber 103 can reliably absorb thestress produced in the radial direction and the axial direction when theFC peripheral equipment 56 is expanded, and achieve improvement in thedurability of the FC peripheral equipment 56.

Further, in the first embodiment, as shown in FIGS. 2, 3 and 5, thereformer 46 includes the annular mixed gas supply chamber 82 a, theannular reformed gas discharge chamber 82 b, the reforming pipes 76, andthe third combustion gas channel 116 c. Mixed gas is supplied to themixed gas supply chamber 82 a, and the produced fuel gas is dischargedto the reformed gas discharge chamber 82 b. The reforming pipes 76 areconnected at one end thereof to the mixed gas supply chamber 82 a, andare connected at the other end thereof to the reformed gas dischargechamber 82 b. The third combustion gas channel 116 c supplies thecombustion gas into the space between the reforming pipes 76.

The evaporator 48 includes the annular water supply chamber 98 a, theannular water vapor discharge chamber 98 b, the evaporation pipes 92,and the fourth combustion gas channel 116 d. Water is supplied to thewater supply chamber 98 a, and water vapor is discharged to the watervapor discharge chamber 98 b. The evaporation pipes 92 are connected atone end thereof to the water supply chamber 98 a, and are connected atthe other end thereof to the water vapor discharge chamber 98 b. Thefourth combustion gas channel 116 d supplies the combustion gas into thespace between the evaporation pipes 92.

The heat exchanger 50 includes the annular oxygen-containing gas supplychamber 70 a, the annular oxygen-containing gas discharge chamber 70 b,the heat exchange pipes 64, and the second combustion gas channel 116 b.Oxygen-containing gas is supplied to the oxygen-containing gas supplychamber 70 a, and the heated oxygen-containing gas is discharged to theoxygen-containing gas discharge chamber 70 b. The heat exchange pipes 64are connected at one end thereof to the oxygen-containing gas supplychamber 70 a, and are connected at the other end thereof to theoxygen-containing gas discharge chamber 70 b. The second combustion gaschannel 116 b supplies the combustion gas into the space between theheat exchange pipes 64.

As described above, the annular supply chambers (mixed gas supplychamber 82 a, water supply chamber 98 a, and the oxygen-containing gassupply chamber 70 a), the annular discharge chambers (reformed gasdischarge chamber 82 b, water vapor discharge chamber 98 b,oxygen-containing gas discharge chamber 70 b), and the pipes (reformingpipes 76, evaporation pipes 92, and heat exchange pipes 64) are providedas a basic structure. Thus, a simple structure can easily be achieved.Accordingly, the production cost of the entire fuel cell module 12 isreduced effectively. Further, by changing various parameters, such asthe volumes of the supply chambers and the discharge chambers, thelength, the diameter, and the number of pipes, a desired operation canbe achieved depending on various operating conditions, and a widervariety of designs becomes available.

Further, the combustion gas flows through the first combustion gaschannel 116 a in the first area R1, then, the second combustion gaschannel 116 b in the second area R2, then, the third combustion gaschannel 116 c in the third area R3, and then, the fourth combustion gaschannel 116 d in the fourth area R4. Thereafter, the combustion gas isdischarged to the exterior of the fuel cell module 12. Thus, it becomespossible to effectively supply the heat to the exhaust gas combustor 52,the heat exchanger 50, the reformer 46, and the evaporator 48 of the FCperipheral equipment 56. Accordingly, improvement in the heat efficiencyis achieved, and thermally self-sustaining operation can be facilitated.

Moreover, the oxygen-containing gas supply chamber 70 a is formedbetween the first inner ring 66 a to which the ends of the heat exchangepipes 64 are inserted and the first outer ring 68 a spaced from thefirst inner ring 66 a. The oxygen-containing gas discharge chamber 70 bis formed between the first inner ring 66 b to which the ends of theheat exchange pipes 64 are inserted and the first outer ring 68 b spacedfrom the first inner ring 66 b. The mixed gas supply chamber 82 a isformed between the second inner ring 78 a to which the ends of thereforming pipes 76 are inserted and the second outer ring 80 a spacedfrom the second inner ring 78 a. The reformed gas discharge chamber 82 bis formed between the second inner ring 78 b to which the ends of thereforming pipes 76 are inserted and the second outer ring 80 b spacedfrom the second inner ring 78 b. The water supply chamber 98 a is formedbetween the third inner ring 94 a to which the ends of the evaporationpipes 92 are inserted and the third outer ring 96 a spaced from thethird inner ring 94 a. The water vapor discharge chamber 98 b is formedbetween the third inner ring 94 b to which the ends of the evaporationpipes 92 are inserted and the third outer ring 96 b spaced from thethird inner ring 94 b.

Therefore, the oxygen-containing gas supply chamber 70 a is formedbetween the first inner ring 66 a and the first outer ring 68 a, theoxygen-containing gas discharge chamber 70 b is formed between the firstinner ring 66 b and the first outer ring 68 b, the mixed gas supplychamber 82 a is formed between the second inner ring 78 a and the secondouter ring 80 a, the reformed gas discharge chamber 82 b is formedbetween the second inner ring 78 b and the second outer ring 80 b, thewater supply chamber 98 a is formed between the third inner ring 94 aand the third outer ring 96 a, and the water vapor discharge chamber 98b is formed between the third inner ring 94 b and the third outer ring96 b. Thus, structure is simplified effectively. Accordingly, theproduction cost of the fuel cell module 12 is reduced effectively, andsize reduction is achieved easily.

Further, the reformed gas discharge chamber 82 b, the water vapordischarge chamber 98 b, and the oxygen-containing gas discharge chamber70 b are provided on one end side close to the fuel cell stack 24,whereas the mixed gas supply chamber 82 a, the water supply chamber 98a, and the oxygen-containing gas supply chamber 70 a are provided on theother end side opposite from the fuel cell stack 24.

In such a structure, reactant gases (fuel gas and oxygen-containinggas), immediately after being raised in temperature and reformingthereof, can be supplied promptly to the fuel cell stack 24. Further,while a decrease in temperature due to radiant heat is minimized,exhaust gas from the fuel cell stack 24 can be supplied to the reformer46, the evaporator 48, the heat exchanger 50, and the exhaust gascombustor 52 of the FC peripheral equipment 56. Accordingly, animprovement in heat efficiency is achieved, and a thermallyself-sustaining operation is facilitated.

Further, in the evaporator 48, at least one of the evaporation pipes 92forms an evaporation return pipe 102, which connects the water vapordischarge chamber 98 b and the mixed gas supply chamber 82 a of thereformer 46. Thus, in a state in which the water vapor is kept hot, thewater vapor is mixed with the raw fuel in the mixed gas supply chamber82 a of the reformer 46 to thereby obtain the mixed gas. Accordingly, animprovement in reforming efficiency is achieved.

Further, the fuel cell module 12 is a solid oxide fuel cell module.Therefore, the fuel cell module 12 is applicable to high temperaturetype fuel cells such as SOFC.

As shown in FIG. 7, a fuel cell system 130 includes a fuel cell module132 according to a second embodiment of the present invention.Constituent elements of the fuel cell module 132 according to the secondembodiment of the present invention, which are identical to those of thefuel cell module 12 according to the first embodiment, are labeled withthe same reference numerals, and descriptions of such features areomitted.

As shown in FIG. 8, the fuel cell module 132 includes a first area R1comprising, e.g., a circular opening where an exhaust gas combustor 52and a start-up combustor 54 are provided, an annular second area R2disposed around the first area R1 where the reformer 46 is provided, anannular third area R3 disposed around the second area R2 where the heatexchanger 50 is provided, and an annular fourth area R4 disposed aroundthe third area R3 where the evaporator 48 is provided.

The stress absorber 103 is provided in at least one of the first areaR1, the second area R2, the third area R3, and the fourth area R4 (inparticular, an area which is likely to be exposed to high heat). In thesecond embodiment, the stress absorber 103 is provided in all of thefirst area R1, the second area R2, the third area R3, and the fourtharea R4. The stress absorber 103 according to the second embodiment hasthe same structure as the stress absorber 103 according to the firstembodiment.

The FC peripheral equipment 56 includes a first partition plate 134 aprovided between the first area R1 and the second area R2, a secondpartition plate 134 b provided between the second area R2 and the thirdarea R3, a third partition plate 134 c provided between the third areaR3 and the fourth area R4, and a fourth partition plate 134 d disposedaround the fourth area R4.

As shown in FIGS. 8 and 9, first combustion gas holes 62 a are providedadjacent to an end of the first partition plate 134 a opposite from thefuel cell stack 24, second combustion gas holes 62 b are providedadjacent to an end of the second partition plate 134 b close to the fuelcell stack 24, third combustion gas holes 62 c are provided near an endof the third partition plate 134 c opposite from the fuel cell stack 24,and fourth combustion gas holes 62 d are provided adjacent to an end ofthe fourth partition plate 134 d close to the fuel cell stack 24.

A plurality of gas extraction holes 136 a are formed in the firstpartition plate 134 a opposite from the first combustion gas holes 62 a.Each of the gas extraction holes 136 a has an opening area, which issmaller than each of the opening areas of the first combustion gas holes62 a. The gas extraction holes 136 a are formed at positions confrontingthe second combustion gas holes 62 b formed in the second partitionplate 134 b. A plurality of gas extraction holes 136 b are formed in thesecond partition plate 134 b at positions confronting the thirdcombustion gas holes 62 c formed in the third partition plate 134 c. Aplurality of gas extraction holes 136 c are formed in the thirdpartition plate 134 c at positions confronting the fourth combustion gasholes 62 d formed in the fourth partition plate 134 d. The gasextraction holes 136 b, 136 c are not essential, and may be providedonly as necessary.

In the second embodiment, the fuel cell module 132 includes the firstarea R1 where the exhaust gas combustor 52 and the start-up combustor 54are provided, the annular second area R2 disposed around the first areaR1 where the reformer 46 is provided, the annular third area R3 disposedaround the second area R2 where the heat exchanger 50 is provided, andthe annular fourth area R4 disposed around the third area R3 where theevaporator 48 is provided.

In this structure, hot temperature equipment with a large heat demandsuch as the reformer 46 (and the heat exchanger 50) are provided on theinside, and low temperature equipment with a small heat demand such asthe evaporator 48 are provided on the outside. Accordingly, animprovement in heat efficiency is achieved, and a thermallyself-sustaining operation is facilitated easily. Further, a simple andcompact structure is achieved.

Further, the stress absorber 103 is provided in at least one of thefirst area R1, the second area R2, the third area R3, and the fourtharea R4. Thus, when the FC peripheral equipment 56 including thereformer 46, the evaporator 48, the heat exchanger 50, the exhaust gascombustor 52, and the start-up combustor 54 is expanded by heat, thestress absorber 103 absorbs the heat stress in the radial direction andthe heat stress in the axial direction. Accordingly, the same advantagesas in the case of the first embodiment are obtained. For example, itbecomes possible to suitably suppress degradation of the durability inthe FC peripheral equipment 56 due to the heat stress.

In particular, since the reformer 46 is provided inside the heatexchanger 50, in an environment where the A/F (air/fuel gas) ratio isrelatively high, the reformer 46, which is suitable for reforming athigh temperature, can be used advantageously.

In the first and second embodiments, the stress absorber 103 includingthe inner curved portions 103 ai, 103 bi and the outer curved portions103 ao, 103 bo each having a semicircular shape in cross section isused. However, the present invention is not limited in this respect.

For example, a stress absorber 140 shown in FIG. 10 includes adecentered curved portion 142 having a semicircular shape with a centerO positionally offset in cross section. The curved portion 142 isapplicable to the inner curved portion and the outer curved portion.

A stress absorber 144 shown in FIG. 11 includes a curved portion 146having a partial oval shape in cross section. The curved portion 146 isapplicable to the inner curved portion and the outer curved portion.

A stress absorber 150 shown in FIG. 12 is provided in an inner ring 152and an outer ring 154. A curved portion 150 a of the stress absorber 150is formed only in the outer position (or inner position) of the innerring 152, and a curved portion 150 b of the stress absorber 150 isformed only in the outer position (or inner position) of the outer ring154.

A stress absorber 160 shown in FIG. 13 is provided in an inner ring 162and an outer ring 164. Inner curved portions 160 ai and outer curvedportions 160 ao of the stress absorber 160 are formed at inner and outerpositions of the inner ring 162. A plurality of, e.g., two inner curvedportions 160 ai curved against each other in a bellows shape, and aplurality of, e.g., two outer curved portions 160 ao curved against eachother in a bellows shape are provided.

Inner curved portions 160 bi and outer curved portions 160 bo of thestress absorber 160 are formed at the inner and outer positions of theouter ring 164. A plurality of, e.g., two inner curved portions 160 bicurved against each other in a bellows shape, and a plurality of, e.g.,two outer curved portions 160 bo curved against each other in a bellowsshape are provided.

Although certain preferred embodiments of the present invention has beenshown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

1. A fuel cell module comprising: a fuel cell stack formed by stackingfuel cells for generating electricity by electrochemical reactionsbetween a fuel gas and an oxygen-containing gas; a reformer forreforming a mixed gas of water vapor and a raw fuel chiefly containinghydrocarbon to produce the fuel gas supplied to the fuel cell stack; anevaporator for evaporating water, and supplying the water vapor to thereformer; a heat exchanger for raising temperature of theoxygen-containing gas by heat exchange with combustion gas, andsupplying the oxygen-containing gas to the fuel cell stack; an exhaustgas combustor for combusting the fuel gas discharged from the fuel cellstack as a fuel exhaust gas and the oxygen-containing gas dischargedfrom the fuel cell stack as an oxygen-containing exhaust gas to therebyproduce the combustion gas; and a start-up combustor for combusting theraw fuel and the oxygen-containing gas to thereby produce the combustiongas, the fuel cell module further comprising: a first area where theexhaust gas combustor and the start-up combustor are provided; anannular second area disposed around the first area where one of thereformer and the heat exchanger is provided; an annular third areadisposed around the second area where another of the reformer and theheat exchanger is provided; an annular fourth area disposed around thethird area where the evaporator is provided; a first partition plateprovided between the first area and the second area; a second partitionplate provided between the second area and the third area; and a thirdpartition plate provided between the third area and the fourth area,wherein a stress absorber for absorbing heat stress is provided in atleast one of the first area, the second area, the third area, and thefourth area.
 2. The fuel cell module according to claim 1, wherein thereformer includes an annular mixed gas supply chamber to which the mixedgas is supplied, an annular reformed gas discharge chamber to which theproduced fuel gas is discharged, and a plurality of reforming pipesconnected at one end to the mixed gas supply chamber, and connected atanother end to the reformed gas discharge chamber, and a combustion gaschannel for supplying the combustion gas to a space between thereforming pipes; the evaporator includes an annular water supply chamberto which the water is supplied, an annular water vapor discharge chamberto which the water vapor is discharged, a plurality of evaporation pipesconnected at one end to the water supply chamber, and connected atanother end to the water vapor discharge chamber, and a combustion gaschannel for supplying the combustion gas to a space between theevaporation pipes; and the heat exchanger includes an annularoxygen-containing gas supply chamber to which the oxygen-containing gasis supplied, an annular oxygen-containing gas discharge chamber to whichthe heated oxygen-containing gas is discharged, a plurality of heatexchange pipes connected at one end to the oxygen-containing gas supplychamber, and connected at another end to the oxygen-containing gasdischarge chamber, and a combustion gas channel for supplying thecombustion gas to a space between the heat exchange pipes.
 3. The fuelcell module according to claim 2, wherein the combustion gas flowsthrough a combustion gas channel in the first area, then, the combustiongas channel in the second area, then, the combustion gas channel in thethird area, and then, the combustion gas channel in the fourth area, andthereafter, the combustion gas is discharged to exterior of the fuelcell module.
 4. The fuel cell module according to claim 2, wherein eachof the mixed gas supply chamber and the reformed gas discharge chamberis formed between an inner ring to which ends of the reforming pipes areinserted and an outer ring spaced from the inner ring; each of the watersupply chamber and the water vapor discharge chamber is formed betweenan inner ring to which ends of the evaporation pipes are inserted and anouter ring spaced from the inner ring; and each of the oxygen-containinggas supply chamber and the oxygen-containing gas discharge chamber isformed between an inner ring to which ends of the heat exchange pipes(64) are inserted and an outer ring spaced from the inner ring.
 5. Thefuel cell module according to claim 4, wherein the reformed gasdischarge chamber, the water vapor discharge chamber, and theoxygen-containing gas discharge chamber are provided on one end sideclose to the fuel cell stack; and the mixed gas supply chamber, thewater supply chamber, and the oxygen-containing gas supply chamber areprovided on another end side opposite from the fuel cell stack.
 6. Thefuel cell module according to claim 5, wherein the stress absorber isprovided in the inner ring and the outer ring of at least one of thereformed gas discharge chamber, the oxygen-containing gas dischargechamber, and the water vapor discharge chamber.
 7. The fuel cell moduleaccording to claim 5, wherein the stress absorber is provided in theinner ring and the outer ring of at least one of the mixed gas supplychamber, the water supply chamber, and the oxygen-containing gas supplychamber.
 8. The fuel cell module according to claim 6, wherein thestress absorber comprises a curved portion provided at least in any ofinner positions or outer positions of the inner ring and the outer ring.9. The fuel cell module according to claim 2, wherein at least one ofthe evaporation pipes forms an evaporation return pipe, which isconnected to the water vapor discharge chamber and the mixed gas supplychamber.
 10. The fuel cell module according to claim 1, wherein the fuelcell module is a solid oxide fuel cell module.